- CT-011 is a humanized immunoglobulin G 1 (IgG1) kappa recombinant monoclonal antibody against PD-1 receptor that blocks the interaction of PD-L1 with PD-1. CT-011 specifically binds to an epitope that is shared between the murine and the human PD-1 receptors on activated T cells, B cells, natural killer (NK) cells, and myeloid cells (CD14+ cells) and primarily functions in effector/memory T lymphocytes and in NK cells. In a functional bioassay, CT-011 was demonstrated to block the activity of PD-1 and to operate on CD4+CD45RO+ effector/memory T lymphocytes leading to attenuation of apoptotic processes.